h--hence called hoop iron. The courses of bricks
where this occurs must be laid in cement, because iron in contact with
cement does not perish as it does in contact with mortar.

If in every story of a building four or five courses are thus laid and
fortified, a great deal of strength is given to the structure. Another
method, which has rather fallen into disuse, is grouting. This is
pouring liquid mortar, about the consistency of gruel, upon the work at
about every fourth course. The result is to fill up all interstices and
cavities, and to delay the drying of the mortar, and brickwork so
treated sets extremely hard. I have seen a wall that had been so treated
cut into, and it was quite as easy to cut the bricks (sound ones though
they were) as the mortar joints.

Grouting is objected to because it interferes with the good look of the
work, as it is very difficult to prevent streaks of it from running down
the face, and it is apt to delay the work. But it is a valuable means of
obtaining strong brickwork. Another and a more popular method is to
build the work in cement, now usually Portland cement. This, of course,
makes very strong, sound work, and does not involve any delay or dirt
like grouting, or the introduction of any fresh material like hoop iron.
But it, of course, adds to the expense of the work considerably, as
cement is much more costly than lime. I ought to add that the advocates
of Scott's selenitic mortar claim that it not only sets quickly and
hard, but that it is extremely tenacious, and consequently makes a much
more robust wall than ordinary mortar. I dare say this is true; but I
have not happened to see such a wall cut into, and this is the best test
of solidity.

The second deficiency in brickwork which I am bound to notice is that,
though it is very fireproof, it is far from being waterproof. In an
exposed situation rain will drive completely through a tolerably stout
brick wall. If water be allowed to drop or fall against it, the wall
will become saturated like a sponge. If the foot of a wall becomes wet,
or if the earth resting against the lower parts of it be moist, water
will, if not checked, rise to a great height in it, and if the upper
part of the wall be wet, the water will sink downward. With most sorts
of brick the outer face absorbs moisture whenever the weather is moist;
and in time the action of the rain, and the subsequent action of frost
upon the moisture so taken up, destroys the